Move templates into their own project, installable via composer

[mapkyca]

Is your feature request related to a problem? Please describe.

Templates are currently hard wired into known, so if you want to set up your own interface (e.g. react) you still need all the php templates. Additionally the only versioning available is with known itself, so themes can quickly break between builds.

Describe the solution you'd like

Install templates from their own package using composer, with an autoloader that registers the template hierarchy with bonita.

This will allow us to quickly roll different builds of Known, using for example a react front end, or introduce a flex box front end (#2325 ) without breaking things. Themes and plugins can specify their own template requirements, meaning composer can do the heavy lifting for us wrt versioning and package management

Probably not a v1.0 thing, even though I believe it'd be pretty straightforward.

[rmdes]

Sounds really cool, not sure how to use this at this stage though..